The present invention generally relates to a switching system for exchanging time-division/multiplex communication information such as a sound and data employing a fixed length cell having a header for a routing. More specifically, the present invention is directed to a switching system suitable for integrating information which is originally suitable to line exchanges of sounds with information which occurs in a burst form, such as data, and for exchanging the information.
In accordance with various needs for terminal units in a network system, a flexible and economical switching system has been required that can integrate the various conditioned data communications. The communications contain not only the typical bit rate of the telephone sound (64 kb/s), but also various bit rates from low velocity data (several hundreds b/s) up to video signals (several Mb/s) and various natures, e.g., burst natures and real-time nature.
With respect to such a demand, there has been proposed, a method for uniformly switching all of information with the employment of cell having a fixed length and a header which contains information for routing. For instance, such an expectable switching method has been proposed by the Applicant in a literature entitled "A Study on an Integrated Switching Network", National Convention Record in commemoration of the 70th anniversary of the foundation of The Institute of Electronics, Information and Communication Engineers of Japan, 1987, switching division 1832. In this example, all of the communication information are transferred by employing the fixed length block referred to as a "cell". This switching system is so constructed as to employ the temporal switch function in every incoming highway in order that a plurality of cells having the same destinations collide with each other within the space-division switch with employment of the header-driver type space-division switch. Further, this temporal switch function includes the memory for the switching purpose and the buffer memory for the queuing so as to handle two modes: the line switched mode such as telephone sounds, (for requiring the real-time nature) and also the burst switched mode by which the data occurring in the burst mode is transferred with a certain amount of delay. The cell for the line switched mode is handled with a priority without processing the cell via the buffer memory in order to guarantee the real time nature, whereas the cell for the burst switched mode is processed when there is queuing in the buffer memory and an empty time slot.
Furthermore, "TDM (time-division modulation) switching system" as other conventional switching system has been described in JP-A-59-135994. In this switching system, although there is no clear description of such an idea to handle the communications containing two different natures, i.e., line switched mode and burst switched mode, another function is introduced for temporarily substituting the fixed length cell with employment of the buffer memory. In this case, the same buffer memory is utilized for the cell queuing and switching. To realize the queuing, the queue unit is employed to store the addresses of the buffer memory by which the cell is written, in accordance with the destinations of the cells.